|Publication number||US6878300 B2|
|Application number||US 10/262,727|
|Publication date||Apr 12, 2005|
|Filing date||Oct 1, 2002|
|Priority date||May 18, 1998|
|Also published as||US6235213, US6478978, US6479393, US6533953, US6800561, US6967170, US20010009245, US20030036286, US20030047537, US20030052089|
|Publication number||10262727, 262727, US 6878300 B2, US 6878300B2, US-B2-6878300, US6878300 B2, US6878300B2|
|Inventors||Tuman Earl Allen, III|
|Original Assignee||Micron Technology, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (59), Non-Patent Citations (4), Referenced by (7), Classifications (15), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This patent resulted from a continuation application of U.S. patent application Ser. No. 09/797,355, filed on Feb. 28, 2001, entitled “Etching Methods, Methods of Removing Portions of Material, and Methods of Forming Silicon Nitride Spacers” and listing T. E. Allen III as inventor, which is a continuation application of U.S. patent application Ser. No. 09/080,656, filed on May 18, 1998, now U.S. Pat. No. 6,235,213, the disclosure of which is incorporated by reference.
The invention pertains to etching methods, such as, for example, methods of forming silicon nitride spacers.
A commonly utilized method for removing at least some of a material is plasma etching. Such method can be used, for example, in semiconductor processing. An enormous diversity of materials can be removed by appropriately adjusting etchant components and etching parameters. Among the materials that can be removed are polycrystalline silicon, silicon nitride and silicon oxides. Etchants that can be utilized for removing polycrystalline silicon include HCl, HBr, HI, and Cl2, alone or in combination with each other and/or one or more of He, Ar, Xe, N2, and O2. A suitable etchant that can be utilized for removing a silicon oxide, such as silicon dioxide, is a plasma comprising CF4/CHF3, or CF4/CH2F2. Additionally, a suitable etchant for removing silicon oxide is a plasma comprising a large amount of CF3, and a minor amount of CH2F3. A suitable etchant for removing silicon nitride is a plasma comprising CF4/HBr.
An example prior art reaction vessel 10 is illustrated in FIG. 1. Reaction vessel 10 comprises a plurality of sidewalls 12 surrounding an internal reaction chamber 14. Also, reaction vessel 10 comprises a radio frequency (RF) generating coil 16 surrounding a portion of reaction chamber 14 and connected to a first RF source 18. RF coil 16 is configured to generate a plasma within reaction chamber 14.
A substrate 20 is received within internal chamber 14 and connected to a second RE source 22. Second RE source 22 is configured to generate an RE bias at substrate 20. Additionally, reaction vessel 10 can comprise coolant coils (not shown) configured to cool a backside of substrate 20 and thereby maintain substrate 20 at a desired temperature during an etching process. It is to be understood that vessel 10 is an exemplary etching vessel. Other constructions are possible. For instance, reaction vessel 10 utilizes a cylindrical inductively driven source geometry, but planar or other inductively driven source geometries can be used. Also, reaction vessel 10 is shown utilizing two separate RF sources, 18 and 22, but other constructions can be used wherein a single RF source can be utilized and the RE power from such source split to form a first RF power at coil 16 and an RE bias at substrate 20.
Substrate 20 can comprise, for example, a monocrystalline silicon wafer. To aid in interpretation of the claims that follow, the term “semiconductive substrate” is defined to mean any construction comprising semiconductive material, including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials thereon), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
In operation, plasma gases (not shown) are flowed into internal chamber 14 and converted into a plasma by energy input from reaction coil 16. An RF bias is generated at substrate 20, and such RF bias draws plasma components to a surface of substrate 20 to etch a material at such surface.
During etching of a component from substrate 20, the materials produced by chemical reaction to the substrate with etch gases are released into the internal chamber. Such materials are referred to herein as etch reaction products, or as etchant debris. A method of determining when an etch has penetrated a material is to monitor the concentration of the evolved reaction products and/or etchant gases as the etch proceeds. Monitoring of the etchant debris can be accomplished by, for example, spectroscopic methods, including, for example, ultraviolet-visible spectroscopy and mass spectrometry. Preferably, the monitoring will be performed by an automated system, with software configured to detect when a concentration of a monitored material decreases within the etchant debris.
In the shown embodiment, a monitoring device 28 is provided to observe etchant debris within reaction chamber 14 through a window 26. Monitoring device 28 can comprise, for example, a spectrometer. The spectrometer can be configured to, for example, display a signal corresponding to a concentration of a particular component in the etchant debris, and/or to send such signal to an automated mechanism which performs a function in response to particular signal characteristics. An example automated system is a system comprising an algorithm to analyze the signal and determine from the analysis when an etch penetrates a particular material. The automated system can be configured to terminate the etching process in response to a determination that the etch has penetrated the particular material.
An etch will frequently be conducted in two distinct etching steps, particularly if the etching is to remove a thickness of material that is greater than or equal to 200 Angstroms. First, a highly physical (non-selective) etch is utilized to etch through the majority of a material. Second, a chemical-type etch (highly selective) is utilized to etch through a remainder of the material. A less selective (physical-type) etch generally has better center-to-edge uniformity than a more selective (chemical-type) etch. Center-to-edge uniformity can be understood by reference to
Physical-type etch processes generally have a high degree of center-to-edge uniformity, and therefore etch edge region 42 at about the same rate as center region 44. In contrast, chemical-type etches typically have a lower degree of center-to-edge uniformity, and accordingly etch edge region 42 at a significantly different rate than center region 44.
A reason for utilizing a physical-type etch initially in an etching process is to maintain a high degree of center-to-edge uniformity as the bulk of a material is etched. The etching process is then changed to a more chemical-type etch as a final portion of the material is removed to obtain a high degree of selectivity for the material relative to other materials that can be exposed during latter stages of an etch.
A chemical-type etch and a physical-type etch can utilize the same etchants but vary in power settings and pressures, or can utilize different etchants at either the same or different power settings and pressures. If the physical-type etch and chemical-type etch comprise the same etchants, the physical-type etch generally comprises a higher bias power at a substrate, and a lower pressure within a reactor than the chemical-type etch. For example, both chemical-type etching and physical-type etching of a silicon nitride material can utilize an etchant comprising CF4/HBr. However, the physical-type etching will utilize an RF power to primary RF coil 16 of from about 250 to about 800 watts, a bias power to substrate 20 of from about 75 to about 400 watts, and a pressure within internal chamber 14 of from about 5 to about 15 mTorr. In contrast, a chemical-type etch will utilize a power to primary RF coil 16 (
A difficulty in etching methods can occur during monitoring of etchant debris. For instance, a nitride spacer etch is described with reference to
The etch of silicon nitride layer 64 comprises two distinct etch steps, an initial physical-type etch, and a subsequent chemical-type etch. The
A difficulty occurs in monitoring peak region 72 to ascertain the precise time at which nitride layer 64 (
In one aspect, the invention encompasses a method of removing at least a portion of a material from a substrate. The material is subjected to a first etching and a second etching in a reaction chamber. A component of the material is removed from at least one sidewall of the reaction chamber between the first etching and the second etching.
In another aspect, the invention encompasses a method of patterning a material over a semiconductive substrate. A layer of first material is formed against a second material and over a semiconductive substrate. The semiconductive substrate comprises a surface having a center and an edge. The first material is subjected to first etching in a reaction chamber. The first etching comprises a first center-to-edge uniformity across the surface of the wafer and comprises a first selectivity for the first material relative to the second material. The first material is subjected to second etching in the reaction chamber. The second etching comprises a second center-to-edge uniformity across the surface of the wafer and comprises a second selectivity for the first material relative to the second material. The second center-to-edge uniformity is less than the first center-to-edge uniformity, and the second selectivity is greater than the first selectivity. A component of the first material is cleaned from at least one sidewall of the reaction chamber between the first etching and the second etching.
Preferred embodiments of the invention are described below with reference to the following accompanying drawings.
This disclosure of the invention is submitted in furtherance of the constitutional purposes of the U.S. Patent Laws “to promote the progress of science and useful arts” (Article 1, Section 8).
It is observed that the sloped trailing edge of prior art peak region 72 (
In accordance with the present invention, a sidewall of the reaction chamber is cleaned prior to an etching of a material within the chamber to reduce or eliminate inadvertent release of components from the sidewalls during the etching of the material. In a preferred embodiment of the invention, a sidewall of a reaction chamber is cleaned after a physical-type etch of a material within the chamber, and before a chemical-type etch of the material within the same chamber.
A sidewall of a reaction chamber can be cleaned by a number of methods. For instance, the sidewall can be subjected to a plasma containing one or more strong oxidants. Suitable plasmas can include, for example, SF6, Cl2 or NF3 in combination with oxygen atoms. More specifically, suitable plasmas can include, for example, SF6/O2, Cl2/O2, or NF3/O3. Suitable etch conditions can comprise, for example, 500 watts of power to a primary RF coil (such as RF coil 16 of the prior art reactor construction of
It is found that cleaning of the sidewalls of a reaction chamber between a physical-type etch and a chemical-type etch can alleviate the monitoring problems discussed above in the “background” section of this disclosure. A graph of nitrogen-component concentration versus time for a silicon nitride etch process conducted in accordance with the present invention is shown in FIG. 6. More specifically,
A difference between the graph of FIG. 6 and that of
The third peak region of the graph of
A comparison of the graph of a process of the present invention in
Although the process described above is described primarily with reference to a method of etching silicon nitride, it is to be understood that the invention has application to many other etch processes. For instance, the invention can be utilized during etching of silicon oxides or other materials. In such etching, a monitored component can be either oxygen or silicon. Additionally, the invention can be utilized during etching of materials that can consist essentially of silicon, such as, for example, polycrystalline silicon, amorphous silicon or monocrystalline silicon. The silicon can be removed from reaction chamber sidewalls by the strongly oxidizing plasmas described above.
In compliance with the statute, the invention has been described in language more or less specific as to structural and methodical features. It is to be understood, however, that the invention is not limited to the specific features shown and described, since the means herein disclosed comprise preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted in accordance with the doctrine of equivalents.
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|U.S. Classification||216/67, 134/22.1, 216/72, 438/719, 438/714, 438/723, 216/79, 438/734, 134/21, 134/1.1, 257/E21.252|
|Cooperative Classification||Y10S438/905, H01L21/31116|
|Sep 22, 2008||FPAY||Fee payment|
Year of fee payment: 4
|Mar 17, 2009||CC||Certificate of correction|
|Nov 26, 2012||REMI||Maintenance fee reminder mailed|
|Apr 12, 2013||LAPS||Lapse for failure to pay maintenance fees|
|Jun 4, 2013||FP||Expired due to failure to pay maintenance fee|
Effective date: 20130412